Potato soup: fast on blood sugar, and safe only if kept cold

In a randomized crossover trial in 20 healthy adults, a soup made with red lentils in place of potato gave a blood glucose response 49 percent of the potato soup at the same 25 g of carbohydrate, and green lentils gave 61 percent. That was a single meal, and the potato soup was the control, so the finding describes potato soup as the faster one. Soup as a starter has better evidence than soup as a dish. In a crossover trial in 60 normal-weight adults, a vegetable soup before a lab lunch cut the whole meal by 20 percent, about 134 calories. That soup was vegetable, not potato, and cream-based soups carry more energy. We found no trial that tested potato soup itself for fullness, weight or blood pressure.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• Homemade potato and leek soup has about 56 calories, 6.2 g carbohydrate, 2.2 g fat, 180 mg potassium and 47 mg sodium per 3.5 oz (100 g) in UK food tables. — UK composition record for homemade potato and leek soup (n = 1 record) Evidence E source
  Per 100 g: 56 calories, carbohydrate 6.2 g, starch 4.7 g, fat 2.2 g, protein 1.5 g, potassium 180 mg, sodium 47 mg, NSP fiber 0.8 g

What a real portion looks like

• US survey data weigh 1 cup of potato soup at 255 g, a single container at 440 g and a can at 525 g. — FNDDS portion weights for potato soup (n = -) Evidence E source
  1 cup 255 g; individual container 440 g; can 525 g; quantity not specified 255 g

What your body absorbs

• In a crossover isotope trial in 37 women, about 25.5% of the zinc in boiled mashed regular potatoes was absorbed. — 37 women aged 18-45, Peruvian highlands, 500 g boiled mashed potatoes twice a day (n = 37) Evidence B source
  Fractional zinc absorption 25.5% (SD 7.0) regular vs 20.8% (SD 5.4) biofortified potatoes

What cooking and storage change

• Observational data from three US cohorts link French fries, but not baked, boiled or mashed potatoes, with higher type 2 diabetes risk. — 205,107 US adults followed 5.2 million person-years (n = 205107) Evidence C source
  Per 3 servings/week: fries HR 1.20 (1.12-1.28); baked, boiled or mashed HR 1.01 (0.98-1.05)

What it does to your health

• In a crossover trial in 60 adults, eating a vegetable soup before lunch cut total meal energy intake by 20%, about 134 calories, whatever the soup's texture. — 60 normal-weight men and women, weekly lab lunches over 5 weeks (n = 60) Evidence B source
  Total meal energy -20% (134 +/- 25 calories) vs no soup
• In a within-subject preload study of 31 young adults, 300-calories soups reduced hunger about as much as the same foods eaten solid, and more than a drink. — 13 men and 18 women, mean age 23.7, mean BMI 23.0, 300 calories preloads (n = 31) Evidence C source
  Soups matched solid foods for hunger and fullness, beverage weakest
• In a crossover trial in 20 adults, swapping the potato in a soup for red lentils lowered the blood glucose response to 49% of the potato soup, at equal carbohydrate. — 20 healthy adults aged 18-40, soups with 25 g available carbohydrate, blood sampled for 2 h (n = 20) Evidence B source
  Relative glycemic response 49% (red lentil) and 61% (green lentil) vs potato soup, p < 0.0001
• Observational data pooled from 103 studies do not link total potato intake with hypertension or diabetes. — 51 articles, 103 observational studies (n = 103 studies) Evidence C source
  Highest vs lowest total potato: hypertension RR 1.07 (0.95-1.21), diabetes RR 1.08 (0.96-1.22)

Safety, limits and interactions

• Two US cases of type A botulism in 2011 followed eating commercial refrigerated potato soup that had been kept unrefrigerated for weeks. — 2 adults, Ohio and Georgia, 2011 (n = 2) Evidence C source
  Botulism requiring antitoxin, one patient ventilated and hospitalized 57 days

Who this works differently for

• In a crossover isotope trial in 28 iron-depleted women, about 16.6% of the iron in regular potato meals was absorbed. — 28 young women with low iron stores, Peruvian highlands, ten 460 g potato meals (n = 28) Evidence B source
  Fractional iron absorption 16.6% (95% CI 14.0-19.6) regular vs 12.1% (10.3-14.2) biofortified

The bottom line

A homemade potato and leek soup in the UK food tables has about 56 calories, 6.2 g of carbohydrate, 2.2 g of fat, 180 mg of potassium and 47 mg of sodium per 3.5 oz (100 g). That is a lightly salted recipe. Canned and restaurant versions usually carry far more sodium and cream. US survey data weigh a cup at 255 g, a single container at 440 g and a can at 525 g, so a whole can is about two cups and the per-cup label doubles. The potato itself gives up its minerals fairly readily. In a stable isotope crossover in 37 women eating 18 oz (500 g) of plain boiled mashed potato twice a day, 25.5 percent of the zinc was absorbed. In 28 young women with low iron stores, 16.6 percent of the iron in regular potato meals was absorbed (95% CI 14.0 to 19.6). Women with low iron stores absorb more than adults whose stores are full, and neither trial served the potato in soup with dairy. On long-term health the data are observational. In three US cohorts of 205,107 adults, every extra three servings a week of French fries went with a 20 percent higher rate of type 2 diabetes (HR 1.20, 95% CI 1.12 to 1.28). Baked, boiled or mashed potatoes showed no significant link (HR 1.01, 0.98 to 1.05). Soup was not studied separately. A pooled analysis of 103 observational studies found no link between total potato intake and hypertension (RR 1.07, 0.95 to 1.21) or diabetes (RR 1.08, 0.96 to 1.22). The real hazard is storage. In 2011 two US adults developed type A botulism after eating commercial potato soup sold from the refrigerated shelf. One had kept it unrefrigerated for 42 days, and one patient needed a ventilator and 57 days in hospital. It is a rare event, but a soup labeled keep refrigerated has to stay in the fridge. We have no data on pregnancy, children or kidney disease for this dish.

Sources

1. psou-r2-01 · dataset
   CoFID 17-831 Soup, potato and leek, homemade: Energy (kcal) 56; Carbohydrate (g) 6.2; Starch (g) 4.7; Fat (g) 2.2; Protein (g) 1.5; Potassium (mg) 180; Sodium (mg) 47; NSP (g) 0.8
   CoFID 2021, Public Health England, code 17-831 Soup, potato and leek, homemade · checked 2026-09-30
2. psou-r2-02 · dataset
   FNDDS 71801000 Soup, potato (fdc_id 2709556): 1 cup 255 g; 1 can 525 g; 1 individual container 440 g; Quantity not specified 255 g
   USDA FNDDS 2021-2023, food code 71801000 Soup, potato (fdc_id 2709556) · checked 2026-09-30
3. psou-r2-06 · RCT (crossover)
   We undertook a single-blinded randomized crossover study (using 67Zn and 70Zn stable isotopes) in which 37 women consumed 500-g biofortified or regular potatoes twice a day. ... Mean fractional zinc absorption (FZA) from the biofortified potatoes was lower than from the regular potatoes, 20.8% (SD: 5.4%) and 25.5% (SD: 7.0%), respectively (P < 0.01).
   J Nutr, 2023 · checked 2026-09-30
4. psou-r2-08 · cohort
   For every increment of three servings weekly of total potato, the rate for T2D increased by 5% (hazard ratio 1.05, 95% confidence interval (CI) 1.02 to 1.08) and for every increment of three servings weekly of French fries the rate increased by 20% (1.20, 1.12 to 1.28). Intake of combined baked, boiled, or mashed potatoes was not significantly associated with T2D risk (pooled hazard ratio 1.01, 95% CI 0.98 to 1.05).
   BMJ, 2025 · checked 2026-09-30
5. psou-r2-03 · RCT (crossover)
   Normal-weight men and women (n = 60) came to the laboratory for lunch once a week for 5 weeks. ... When soup was consumed, subjects reduced meal energy intake by 20% (134+/-25 kcal; 561+/-105 kJ).
   Appetite, 2007 · checked 2026-09-30
6. psou-r2-04 · preload study
   A within-subject design, preload study was administered to 13 male and 18 female adults (23.7+/-0.9 years old) with a mean body mass index (BMI) of 23.0+/-0.7 kg/m2. ... The soups led to reductions of hunger and increases of fullness that were comparable to the solid foods. The beverage had the weakest satiety effect.
   Physiol Behav, 2005 · checked 2026-09-30
7. psou-r2-05 · RCT (crossover)
   In randomized, crossover studies, healthy adults consumed foods containing 25 g AC from green lentils, red lentils or a control (wheat muffin, n = 24; rice chili, n = 24; potato soup, n = 20). ... The RGR for muffins, chilies and soups was 88, 58 and 61%, respectively, for green lentils, and 84, 48 and 49%, respectively, for red lentils.
   Nutrients, 2024 · checked 2026-09-30
8. psou-r2-09 · observational meta-analysis
   Comparing the highest with the lowest categories of total potato intake, total potato intake was not associated with hypertension (summary RR = 1.07; 95% CI: 0.95, 1.21), diabetes (1.08; 95% CI: 0.96, 1.22)
   Nutr Rev, 2025 · checked 2026-09-30
9. psou-r2-10 · case series
   In January and April 2011, CDC provided antitoxin for treatment of two persons with toxin type A botulism associated with consumption of potato soup produced by two companies. ... The soup had been purchased on December 7, 2010, from the refrigerated section of a local grocer, but it had been kept unrefrigerated for 42 days.
   MMWR Morb Mortal Wkly Rep, 2011 · checked 2026-09-30
10. psou-r2-07 · RCT (crossover)
    Women (n = 28; mean ± SD plasma ferritin 21.3 ± 3.3 μg/L) consumed 10 meals (460 g) of both potatoes, each meal extrinsically labeled with either 58Fe sulfate (biofortified) or 57Fe sulfate (nonfortified), on consecutive days. ... Geometric mean (95% CI) fractional iron absorption from the iron-biofortified clone and the nonbiofortified variety were 12.1% (10.3%-14.2%) and 16.6% (14.0%-19.6%), respectively (P < 0.001).
    J Nutr, 2023 · checked 2026-09-30